Abstract
Two-in-tandem circular cylinders are an important combination, which is widely encountered in several areas such as flow around bridge piers and vegetated open channel flow. One of typical Japan-river characteristics is the sudden change of discharge due to big amount of rainfalls so that the bridge piers are affected by surrounding instantaneous flows such as separated and wake flows which lead to the serious scouring problem. In order to reveal such kind of flow effects, flow visualization around two-in-tandem cylinders is conducted under non-submerged condition in the present study by means of particle tracking velocimetry (PTV), which is developed to estimate more accurate velocity under conditions of large-velocity difference. In addition, the POD analysis of typical fluctuating pattern, spectral analysis and conditional sampling analysis are applied to reveal the coherent structures.
